This invention relates to interferometric patterning.
Interference patterns of alternating bright and dark lines are used to expose photo-resists to test their quality and to determine the resolution that can be achieved. Optical schemes for generating interference patterns are illustrated in FIG. 1a and FIG. 1b. In FIG. 1a, an arrangement known as Young""s configuration, two overlapping beams 106 and 108 of plane waves generate interference patterns on a substrate 102. In FIG. 1b, an arrangement known as a Lloyd""s mirror, a plane mirror 104 is used to divert a portion of a beam 110 such that it interferes with another portion to produce interference patterns on substrate 102.
The exposed photo-resist has line structures with a pitch, p, given by p=xcex/(2xc3x97sin [xcex8]), where xcex is the wavelength of the plane waves and xcex8 is the half-angle of convergence. This pitch increases with wavelength. The line size is set by selection of the amount of time and intensity of exposure. A higher amount of exposure results in a smaller line width when using a positive tone photo-resist (i.e., a resist having the portions exposed to light removed after development).
Typically, coherent light sources are used to generate the interference patterns since interfering waves must be spatially and temporally coherent.